A quick note about what the Oracle TRUNC function can do:
If you have a table ORDERS with a date field DATE_CREATION and you want to filter the records with a given date, you can use the TRUNC function.

This will truncate the time from the DATE_CREATION and leave out only the date.
The full syntax for TRUNC is:

TRUNC ( date, [ format ] )date is the date to truncate.format is the unit of measure to apply for truncating. If the format parameter is omitted, the TRUNC function will truncate the date to the day value, so that any hours, minutes, or seconds will be truncated off.techonthenet.com

Update, 28/feb/2014: Another Oracle goodie – how to find out details about sequences: